19-2095; Rev 0; 8/01 High-Current VCOM Drive Buffer Features ♦ Stable with 0.47µF to Unlimited Amount of Output Capacitance ♦ Over 500mA Peak Drive Current ♦ Excellent Settling Characteristics with Capacitive Load ♦ +4.5V to +13V Input Supply ♦ 0.45mA Quiescent Current ♦ Thermal Fault Protection ♦ Thin SOT23-5 Package (1.1mm max) Ordering Information Applications Notebook LCD Panels Monitor LCD Panels PART TEMP. RANGE PIN-PACKAGE TOP MARK MAX1886EZK -40°C to +85°C 5 Thin SOT23-5* ADQL *Requires a special solder temperature profile described in the Absolute Maximum Ratings section. Pin Configuration Typical Operating Circuit TOP VIEW VCC OUT 1 5 FB- 4 FB+ VREF FB+ OUT FB- GND MAX1886 VO GND 2 MAX1886 VCC 3 THIN SOT23-5 ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX1886 General Description The MAX1886 is a high-current operational transconductance amplifier. The MAX1886 is ideal for driving the backplane of an active matrix, dot inversion thin film transistor (TFT) liquid crystal display (LCD). The MAX1886’s high >500mA peak-current drive capability provides fast response to pulsed load conditions. The MAX1886 is stable from 0.47µF to an unlimited amount of output capacitance. The MAX1886 is available in the low-profile (1.1mm max) 5-pin Thin SOT23 package and fully specified over the -40°C to +85°C extended temperature range. MAX1886 High-Current VCOM Drive Buffer ABSOLUTE MAXIMUM RATINGS VCC to GND ............................................................-0.3V to +14V FB-, FB+, OUT to GND...............................-0.3V to (VCC + 0.3V) Continuous Power Dissipation (TA = +70°C) 5-Pin Thin SOT23 (derate 7.1mW°C above +70°C) .....727mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device can be exposed to during board level solder attach and rework. Maxim recommends the use of the solder profiles recommended in the industry-standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and convection reflow processes. Preheating, per this standard, is required. Hand or wave soldering is not recommended. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VCC = 10V, FB- = OUT, VFB+ = 5V, COUT = 0.47µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL VCC Input Supply Range VCC VCC Supply Current ICC Input Offset Voltage VOS Input Bias Current IBIAS CONDITIONS MIN 450 VFB+ = +5V, no load µA mV 5 nA -100 100 nA |VOS| < 10mV over CMR 1.2 VCC 1.2V V +1.2V < VCM < +8.8V VCM Power-Supply Rejection Ratio PSRR +4.5V < VCC < +13V, VFB+ = +2.25V 70 Common-Mode Rejection Ratio CMRR +1.2V < VCM < +8.8V 70 Gain-Bandwidth Product GBW Small signal dB 1/6πCL Small signal (±1mV overdrive) 0.3 Large signal (±30mV overdrive) 10 ±100mV overdrive, VOUT = 3V or 7V IOUT V 900 100 Common-Mode Input Range Output Current Drive UNITS 13 -5 IOS gm MAX -100 Input Offset Current Transconductance TYP 4.5 TA = -40°C to +85°C ±175 TA = 0°C to +85°C ±250 ±550 S mA Thermal Shutdown 170 °C Thermal Shutdown Hysteresis 15 °C Note 1: The MAX1886 is 100% production tested at TA = +25°C. Specifications over temperature are guaranteed by design. SUPPLY VOLTAGE REFERENCE VOLTAGE 3 4 0.47 2 0.47 5 VX 1 MAX1886 RL CL Figure 1. Load Transient Test Circuit 2 Hz _______________________________________________________________________________________ High-Current VCOM Drive Buffer INPUT OFFSET VOLTAGE DEVIATION vs. TEMPERATURE 0.2 0.02 0.1 0 0 ∆VOS (mV) -0.02 -0.04 -0.1 -0.2 -0.06 -0.08 -0.3 -0.10 -0.4 6 7 8 9 10 11 12 13 14 2 TA = +85°C 0 -40 -15 10 35 60 85 -40 -30 -20 -10 0 10 20 TEMPERATURE (°C) OUTPUT CURRENT (mA) SUPPLY CURRENT vs. SUPPLY VOLTAGE NO-LOAD SUPPLY CURRENT vs. TEMPERATURE LOAD TRANSIENT ±10V 0.9 0.8 SUPPLY CURRENT (mA) +25°C 0.4 0.3 1.0 MAX1886 toc04 +85°C -40°C 0.2 0.6 0.4 8.5 10.5 IOUT 500mA/div 0.3 VX 10V/div RL = 2.5Ω, CL = 100nF, FIGURE 1 0 6.5 40 VOUT 200mV/div AC-COUPLED 0.5 0.1 0 30 0.7 0.2 0.1 4.5 TA = +25°C 3 VCC (V) 0.6 0.5 TA = -40°C 4 MAX1886 toc06 5 5 1 MAX1886 toc05 4 6 -40 12.5 -15 10 35 60 85 4µs/div TEMPERATURE (°C) SUPPLY VOLTAGE (V) SHORT-CIRCUIT WAVEFORMS MAX1886 toc07 VOS (mV) 0.04 SUPPLY CURRENT (mA) VCC = 10V VCM = VCC/2 0.3 MAX1886 toc03 0.06 0.4 TRANSCONDUCTANCE (S) VCM = VCC/2 0.08 MAX1886 toc01 0.10 TRANSCONDUCTANCE vs. OUTPUT CURRENT MAX1886 toc02 INPUT OFFSET VOLTAGE DEVIATION vs. SUPPLY VOLTAGE ICC 500mA/div IOUT 500mA/div VOUT 5V/div VCC 5V/div 20ms/div _______________________________________________________________________________________ 3 MAX1886 Typical Operating Characteristics (VCC = 10V, COUT = 1µF, VCM = 5V, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC = 10V, COUT = 1µF, VCM = 5V, TA = +25°C, unless otherwise noted.) SUPPLY CAPACITOR CHARGING CURRENT ICC 500mA/div ICC 500mA/div VCC 10V/div VCC 10V/div VFB+ 5V/div VFB+ 5V/div VOUT 5V/div COUT = 0.47µF MAX1886 toc09 STARTUP WAVEFORMS WITH SOFT-START STARTUP WAVEFORM WITHOUT SOFT-START MAX1886 toc08 MAX1886 High-Current VCOM Drive Buffer VOUT 5V/div COUT = 0.47µF 500µs/div 5µs/div Pin Description PIN NAME DESCRIPTION 1 OUT Output of Buffer Amplifier. Requires a minimum 0.47µF ceramic filter capacitor to GND. Place the capacitor close to OUT. 2 GND Ground 3 VCC Voltage-Supply Input. Bypass to GND with a 0.47µF capacitor close to the pin. Use the output capacitor of the preceding voltage regulator as the additional filter capacitor. 4 FB+ Noninverting Input to Buffer Amplifier 5 FB- Inverting Input to Buffer Amplifier. Feedback must be taken from the output filter capacitor terminal. Detailed Description The MAX1886 operational transconductance amplifier (OTA) provides high-current output that is ideal for driving capacitive loads such as the backplane of a TFT LCD panel. The positive feedback input, FB+, allows common-mode biasing to mid-supply, or other VCOM voltage. The MAX1886 unity-gain bandwidth is GBW = gm/COUT where g m is the amplifier’s transconductance. Transconductance is the ratio of the output current to the input voltage. The gain of the amplifier is dependent upon the load. The MAX1886 requires only a small 0.47µF ceramic output capacitor for stability. The bandwidth is inversely proportional to the output capacitor, so large capacitive loads improve stability; however, lower bandwidth decreases the buffer’s transient response time. To improve the transient response 4 times, the MAX1886’s transconductance increases as the output current increases (see Typical Operating Characteristics). Applications Information Output Filter Capacitor The MAX1886 requires a minimum of 0.47µF output capacitance placed close to OUT. To ensure buffer stability, the output capacitor ESR must be 50mΩ or lower. Ceramic capacitors are an excellent choice. Input Bypass Capacitor The MAX1886 requires a 0.47µF input bypass capacitor (C2) close to the VCC supply input (see Figure 2). Place the MAX1886 close to the preceding voltage regulator output capacitor so that the MAX1886 shares the same capacitor (C1). Minimize trace length and use wide _______________________________________________________________________________________ High-Current VCOM Drive Buffer SWITCHING REGULATOR MAX1886 VIN SOURCE DRIVER VOLTAGE C1 PC BOARD PARASITICS 3 LINEAR REGULATOR C2 0.47µF 4 2 OPTIONAL REFERENCE VOLTAGE CIRCUIT 0.47µF 5 1 GAMMA CORRECTION REFERENCE VOLTAGE TO LCD BACKPLANE MAX1886 Figure 2. Typical TFT LCD Backplane Drive Circuit traces between the voltage regulator output and the MAX1886 V CC input to reduce PC board parasitics (inductance, resistance, and capacitance), which can cause undesired ringing. Voltage Reference The reference voltage for the MAX1886 input can be produced using the output of a linear regulator. The linear regulator will reject the ripple voltage produced by the source drivers (see Figure 2). The output of this linear regulator can also be used for the gamma correction reference voltage. Chip Information TRANSISTOR COUNT: 121 PROCESS: BiCMOS _______________________________________________________________________________________ 5 High-Current VCOM Drive Buffer MAX1886 Package Information 6 _______________________________________________________________________________________ High-Current VCOM Drive Buffer Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 7 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX1886 Package Information (continued)